When Jane and Toz Spalding saw the damaged privacy wall at the Foothills home they wanted to buy, they knew one thing for sure.
No way were they going to cut down the giant mesquite to save the wall.
“We love the tree absolutely,” Jane Spalding says of the 25- or 30-year-old tree with a soaring crown that shades the entire west entrance to the house.
Its trunk is about 1.5 feet in diameter and the tree is about 40 feet tall.
“We never thought of anything but doing the best for this tree,” Spalding says.
The couple called arborist Rick Allen, local manager of Bartlett Tree Experts. Apparently, Allen told them, in an effort to remain stable, the tree grew thick surface and shallow roots that ran right smack into and just under the 4-foot wall that was 6 feet from the trunk.
Those roots lifted the wall, creating cracks and threatening a water pipe that already had been replaced because of tree damage.
The previous homeowners — the Spaldings bought the house in September — responded by continually patching the wall and putting the pipe above the footer anchoring the wall.
“What we saw were repairs designed to keep the wall from falling over,” Spalding says.
They decided to take a different approach. They called landscape designer Paul Connolly, owner of Sundrea Design Studio, to see how they could save both the hardscape and the tree.
Instead of moving or taking down the wall, Connolly suggested cutting out the damaged section and replacing it with a wrought iron fence.
The fence mimics the design of the front gate and matches similar fencing at other homes on the street. The new design fit right in with the look of the neighborhood.
The fence is bolted at both ends to the existing wall. That creates a clear and open path under it for the tree to keep its roots extended. And the Spaldings were able to keep most of the privacy wall.
Long-time neighbors have told the Spaldings they appreciate their efforts to save the tree. A few trees in the neighborhood have been lost in the battle with hardscapes.
“We understand that this is a very old tree and it’s performing an amazing function,” says Spalding. “It’s an amazing showpiece in our front yard.”
TREE VS. HARDSCAPE
Trees damage walls, sidewalks, driveways, patios and homes because they’re acting like, well, trees, says Allen, a certified master arborist. Their roots grow in ways to make them stable and to reach water sources.
Surface and shallow roots occur for many reasons, he says.
If planted improperly, a growing tree will develop strong surface anchors to stay upright in wind.
Trees find and tap into condensation that regularly forms under driveways, sidewalks and patios. They also find undetected slow leaks under a house.
Trees also will tap into shallow, frequent irrigation necessary for lawns.
Caliche gets in the way of developing deep roots.
Gardeners don’t encourage deep root growth. Instead of using flood irrigation, they rely on surface soaking from inadequate drip irrigation.
Once shallow and surface roots develop under hardscape, it’s only a matter of time before they cause damage. “Over time, feeder roots the (circumference) size of a toothpick grow to the size of a (soda) can,” Allen says.
Careful root pruning can save a tree that’s causing damage, he says. It’s possible to remove the offending root and then use a root barrier to keep roots from growing toward the damaged hardscape.
The same idea — severing roots and stopping growth with a root barrier — can be used on whole sections of small roots before they damage hardscape.
However, he says, roots can’t always be cut back because stunted roots make the tree unstable. That makes it easier for wind to topple a tree. It also forces the tree to grow more surface roots.
If possible, it’s better to change the hardscape than cut the tree roots, Allen says.
“It’s better finding something to accommodate the roots, letting the root do the root thing,” Allen says.
He’s seen one homeowner put a small hole in a brick patio wall to let a tree root freely grow through it.
Landscape designer Connolly likes to design ways to separate roots from hardscape.
For instance, if roots threaten a solid concrete walkway, break up the walkway into a stepping-stone design. That allows roots to extend between the stones.
Bridges over roots also keep walkways intact without harming the tree, he says.
Whatever the challenge, it will take some time and thought to find a solution, he says. It’s worth it to save trees that provide shade and a home for wildlife while beautifying the neighborhood.
“Maybe the tree’s not the problem,” he says. “Maybe what’s around it is the problem.”
Contact Tucson freelance writer Elena Acoba at firstname.lastname@example.org